Non-aqueous detergent liquids have been proposed for a number of uses, such as fabric washing and dish-washing. They have advantages over powder products in that they are more rapidly dispersed in water. Further advantages over powder products are the possibility of automatic dosing and higher obtainable product densities resulting in lower transportation and packaging costs.
Non-aqueous detergent liquids have advantages over aqueous liquid products in that they are capable of including water-sensitive ingredients such as bleaches.
With regard to the use in industrial washing machines of non-aqueous liquid detergent composition containing a particulate solid phase dispersed in a liquid phase, it is important that the viscosity of such compositions should be as low as possible whilst still maintaining acceptable stability against separation of the suspended particulate solid material. The reason is that products used in industrial washing machines are usually pumped through long supply lines from the dosing equipment to the point of use inside the washing machine.
It has been described in WO 91/00282 that non-aqueous liquid detergent compositions comprising sodium metasilicate, having an improved stability against sedimentation of the particulate solid material suspended therein and having a reduced tendency to clear layer separation upon storage, can be formulated by including therein a metal oxide having a bulk density of 200 to 1000 g/l.
Detergent compositions suitable for use in industrial washing machines generally contain a considerable level of material which gives a high alkalinity in the wash liquor. This type of material is often referred to as either buffer salt or alkalinity booster, It is known that sodium metasilicate may effectively perform the function of both builder material and alkalinity booster. Therefore, sodium metasilicate is a preferred component of industrial detergent products. However, we have found that only anhydrous sodium metasilicate as a constituent of a non-aqueous liquid composition has resulted in a non-aqueous liquid with an acceptable viscosity so that it can be dosed without having to use complicated apparatus. Moreover, an acceptable viscosity of such non-aqueous liquids containing anhydrous sodium metasilicate could only be obtained at relatively low levels of particulate solids dispersed therein.
Hitherto, only crystalline forms of sodium metasilicate containing less than 5% by weight of water were applied in non-aqueous detergent product formulations. The use of an amorphous form of sodium metasilicate as a particulate solid constituent of a non-aqueous detergent liquid was considered undesirable because of the difficulty of milling non-aqueous liquids containing such sodium metasilicate. Therefore, this type of sodium metasilicate has never been used.
However, it has now surprisingly been found that incorporation of anhydrous substantially amorphous sodium metasilicate into a non-aqueous liquid detergent product results in a low viscosity, pourable, easy to process formulation. Furthermore, we have found that the use of anhydrous substantially amorphous sodium metasilicate as a component of non-aqueous liquids allows a larger amount of solids to be incorporated for obtaining formulations with a good viscosity and stability against sedimentation. In this context, substantially amorphous sodium metasilicate is defined as material which when using light or electron microscopy reveals little if any visual indication of crystals. More precisely defined, it is material that shows at most 10% by weight of material having crystalline order when applying X-ray crystallography techniques.